Fingerprint scanners are the most widely used form of personal biometric today, due largely to their small size and ease of use. A person simply places his finger on the reader, and he is either granted or denied access. In this section, we will examine the operation of the fingerprint scanner at the device and analysis levels so that technology selection and implementation decisions can be made with better awareness of possible limitations.
At the very beginning, the reader needs to be cautioned that the degree to which a person's fingerprint templates (the recorded characteristics of the finger) are protected while being stored by the operating system may create an easier attack point than trying to break the system by creating a fake fingerprint. These biometric fingerprint scanners should be used with careful attention paid to encryption and protection of the user fingerprint templates. Failure to do so will directly affect the strength of protection offered by the system.
With this caveat in mind, we will examine the four broad classes of fingerprint scanners. The most common class is the optical fingerprint scanner. A second type of reader is the ultrasonic fingerprint scanner; it employs ultrasound to capture the fingerprint. A third class of device is the capacitance fingerprint scanner. And a fourth employs an E-field technology to read the fingerprint. All of these approaches are described in this chapter.